Any Ideas for Fuel Calculations

[tcrobine]

Does anyone have a rule of thumb for calculating fuel /diesel required. We have an Antares 760 / fuel tank capacity 220lts / engine Volvo 200hp/ Cruising speed 16kts. The planned journey is from the River Orwell to St Katherines London, probadly about 90 miles. Any ideas would be appreciated.

 

[BAtoo]

Suggest you ask on the mobo forum... or the previous owner/agent if new... but it is about 90 miles!!!

 

[EdEssery]

For diesel engines, very roughly 1 litre per hour per 10HP...

 

[Evadne]

That sounds a tad low. I've been told 1 gallon per 20hp, and my 1GM7 (6.5hp?) uses about 2.5 pints/hour which is pretty damned close to that. Depends on whether you're running at cruising revs or not, and how many engines you have.

 

[chuckaduck]

http://www.passageplan.com/

 

[Whitelighter]

Surely it will be different for a planing hull (going over the water) and a displacement hull (going through the water)?

 

[PCUK]

It doesn't matter to the engine what the boat is doing. If it is producing 20hp it will use on egallon per hour. If it is a turbo it will manage 23 hp per gallon. 1 litre per 10hp is way out.
Cruising speed 16 knots, asuming 3/4 throttle, producing say 150hp, will then use 7.5 gallons per hour. Say 6 hours running. 7.5 X 6 = 45 gallons used X 4.5 = 202 litres.
Best take some Jerry cans along!!!
Check propeller curve for consumption at cruising revs for more accurate forecast.

 

[Whitelighter]

Ok, so my Turbo charged Volvo KAD 43's are 230hp each. So at WOT they should each be sucking 10 gallons each hour. 20 gallons across both engines, or 90.8 litres. As an average however, my cruising speed is about 24knts, which is about 70% throttle, but over the journy's I have made they only seem to be burning 44/45 litres an hour!!!

Also, doesn't load come into it? If you sit your car on the drive and hold the throttle open at 3000rpm you will use less fuel then going up a hill at 3000 rpm. So surely there is an element of dray on the hull/drive/prop that dictates consumption as well as the load (smaller prop/lower gear ratio).

To say all engines use 1 gallon per 20/23 hp is surely way to simplistic. Or have I mis-understood something? /forums/images/graemlins/confused.gif

 

[reeac]

That's what they use. It's 20 bhp hours per gallon. The unknown quantity is the horsepower that you'll be using at any given speed but that's simply a function of propellor revs., not throttle position. Two thirds of max. revs. will require approx. 8/27 of max. power ie. 60bhp or 3 gallons per hour per engine. That's assuming that the prop. is sized correctly such that the engines can just about attain max. revs when in gear.